Glycogen storage disease type 2, also known as Pompe disease or acid maltase deficiency disease, is an inheritedmetabolic disorder caused by an inborn lack of the enzyme acid alpha-glucosidase (also known as acid maltase), which is necessary to break down glycogen, a substance that is a source of energy for the body. This enzyme deficiency causes excess amounts of glycogen to accumulate in the lysosomes, which are structures within cells that break down waste products within the cell. This accumulation of glycogen in certain tissues, especially muscles, impairs their ability to function normally.[1][2] Glycogen storage disease type 2 is a single disease continuum with variable rates of disease progression.[1] In 2006, the U.S. Food and Drug Administration (FDA) approved the enzyme replacement therapy Myozyme as a treatment for all patients with glycogen storage disease type 2.[1][3] Another similar drug called Lumizyme has recently been approved for the treatment this disease.[3][4]

The classic infantile form of glycogen storage disease type 2 is characterized by severe muscle weakness (myopathy) and abnormally diminished muscle tone (hypotonia) without muscle wasting, and usually manifests within the first few months of life. Additional abnormalities may include enlargement of the heart (cardiomegaly), the liver (hepatomegaly), and/or the tongue (macroglossia).[1] Affected infants may also have poor feeding, failure to gain weight and grow at the expected rate (failure to thrive), breathing problems, and hearing loss. Most infants with glycogen storage disease type 2 cannot hold up their heads or move normally. [2] Without treatment, progressive cardiac failure usually causes life-threatening complications by the age of 12 to 18 months.[1][2]

The non-classic infantile form of glycogen storage disease type 2 usually presents within the first year of life. Initial symptoms may include delayed motor skills (crawling, sitting) and myopathy. Cardiomegaly may be present, but unlike the classic infantile form, cardiac failure does not typically occur. Muscle weakness may lead to serious, life-compromising breathing problems by early childhood.[2][5]

In the late onset form of glycogen storage disease type 2, symptoms may not be evident until childhood, adolescence, or adulthood. This form is usually milder than the infantile-onset form of the disorder. Most individuals experience progressive muscle weakness, especially in the legs and the trunk, including the muscles that control breathing.[2]

Last updated: 6/20/2016

The Human Phenotype Ontology (HPO) provides the following list of features that have been reported in people with this condition.
Much of the information in the HPO comes from Orphanet, a European rare disease database. If available, the list includes a rough estimate of how common a feature is (its frequency).
Frequencies are based on a specific study and may not be representative of all studies. You can use the MedlinePlus Medical Dictionary for definitions of the terms below.

Mutations in the GAAgene cause glycogen storage disease type 2. The GAA gene provides instructions for producing an enzyme called acid alpha-glucosidase (commonly called acid maltase). This enzyme is active in lysosomes, which are structures that serve as the cell's recycling center. The enzyme normally breaks down glycogen into a simpler sugar called glucose, which is the main energy source for most cells. Mutations in the GAA gene prevent acid alpha-glucosidase from breaking down glycogen, allowing it to build up in the body's cells. Over time, this buildup damages cells throughout the body, particularly muscle cells.[2]

Glycogen storage disease type 2 is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.[2]

Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.

Testing Resources

The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.

Management Guidelines

The American College of Medical Genetics (ACMG) provides education, resources, and a voice for the medical genetics profession. To make genetic services available to and improve the health of the public, the ACMG promotes the development and implementation of methods to diagnose, treat and prevent genetic diseases. In an effort to fulfill its mission, the ACMG performs many tasks, including developing clinical practice guidelines. In May 2006, the ACMG Work Group on Management of Pompe Disease released a ACMG Practice Guideline titled "Pompe disease diagnosis and management guideline." To view this practice guideline, visit the link above.

The NORD Physician Guide for Glycogen storage disease type 2 was developed as a free service of the National Organization for Rare Disorders (NORD) and it's medical advisors. The guides provide a resource for clinicians about specific rare disorders to facilitate diagnosis and treatment of their patients with this condition.

FDA-Approved Treatments

The medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of this condition.
Learn more orphan products.

Recombinant human acid alpha-glucosidase; alglucosidase alfa(Brand name: Lumizyme) - Manufactured by Genzyme CorporationFDA-approved indication: Lumizyme for patients 8 years and older with late (non-infantile) onset Pompe disease (GAA deficiency) who do not have evidence of cardiac hypertrophy. The safety and efficacy of Lumizyme (alglucosidase alfa) have not been evaluated in controlled clinical trials in infantile-onset patients, or in late (non-infantile) onset patients less than 8 years of age.National Library of Medicine Drug Information Portal

Recombinant human acid alpha-glucosidase(Brand name: Myozyme®) - Manufactured by Genzyme CorporationFDA-approved indication: For use in patients with Pompe disease (GAA deficiency). Alglucosidase alfa has been shown to improve ventilator-free survival in patients with infantile onset Pompe disease as compared to an untreated historical control, whereas use of Alphaglucosidase in patients with other forms of Pompe disease has not been adequately studied to assure safety and efficacy.National Library of Medicine Drug Information Portal

Research helps us better understand diseases and can lead to advances in diagnosis and treatment. This section provides resources to help you learn about medical research and ways to get involved.

Clinical Research Resources

ClinicalTrials.gov lists trials that are studying or have studied Glycogen storage disease type 2. Click on the link to go to ClinicalTrials.gov to read descriptions of these studies.

Please note: Studies listed on the ClinicalTrials.gov website are listed for informational purposes only; being listed does not reflect an endorsement by GARD or the NIH. We strongly recommend that you talk with a trusted healthcare provider before choosing to participate in any clinical study.

The Lysosomal Disease Network is a team of doctors, nurses, research coordinators, and research labs throughout the U.S., working together to improve the lives of people with this condition through research. The Lysosomal Disease Network has a registry for patients who wish to be contacted about clinical research opportunities.

Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

In-Depth Information

Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.

The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.

Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine.

Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.

PubMed is a searchable database of medical literature and lists journal articles that discuss Glycogen storage disease type 2. Click on the link to view a sample search on this topic.

Press Releases

The U.S. Food and Drug Administration (FDA) provides information about an FDA-approved treatment for Pompe disease called Myozyme through a 2006 Press Release. To view this information, click on the above link.

NCATS Co-Sponsored Conferences

Description: The main goal of the Lysosomes and Endocytosis GRC is to foster the dissemination of current research results and the establishment of new research areas and new collaborations in the area of the cell biology of endocytosis, lysosomes, endosomes and related organelles. We hope that many of these new directions and collaborations will be directed toward the etiology, diagnosis and treatment of rare genetic diseases such as lysosomal storage disorders, Hermansky-Pudlak syndrome, Chediak-Higashi syndrome, Niemann Pick disease and tuberous sclerosis, among others.

Description: The specific aims of this meeting were to (1) emphasize the strategies for, and identify the obstacles to, moving from translational research to clinical trials; (2) coalesce members of the LD network into functional research collaborations and present to the LDN community progress on the specific projects that are part of the funded U54 RDCRN grant; (3) foster interdisciplinary collaboration with the overall goal of improving knowledge of basic discoveries and clinical manifestations of these diseases; (4) provide an educational forum for young investigators, clinicians, and researchers in the field; (5) identify and discuss the latest findings in the natural history of lysosomal diseases, diagnostic testing and screening, and treatment, with specific focus on (a) inflammatory components of lysosomal diseases and autophagy, especially in the central nervous system, (b) new treatments of the central nervous systems, and (c) ethics and efficacy in treating the presymptomatic or asymptomatic patient; and (6) identify areas requiring additional basic and clinical research and public policy and regulatory attention, such as ethics and economics, and factors that impact implementation of therapy, including newborn screening.

Contact:
Dr. Danilo A. Tagle(301) 496-5745tagled@mninds.nih.gov

Co-funding Institute(s):
National Institute of Neurological Disorders and Stroke, Office of Rare Diseases Research

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